/*
 * Copyright 2010 LinkedIn Corp.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package cn.shuangbofu.rhea.job.job.shell;

import com.google.common.base.Joiner;
import com.google.common.collect.Iterators;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * A circular buffer of items of a given length. It will grow up to the give size as items are
 * appended, then it will begin to overwrite older items.
 *
 * @param <T> The taskType of the item contained.
 */
public class CircularBuffer<T> implements Iterable<T> {

    private final List<T> lines;
    private final int size;
    private int start;

    public CircularBuffer(int size) {
        lines = new ArrayList<>();
        this.size = size;
        start = 0;
    }

    public void append(T line) {
        if (lines.size() < size) {
            lines.add(line);
        } else {
            lines.set(start, line);
            start = (start + 1) % size;
        }
    }

    @Override
    public String toString() {
        return "[" + Joiner.on(", ").join(lines) + "]";
    }

    @Override
    public Iterator<T> iterator() {
        if (start == 0) {
            return lines.iterator();
        } else {
            return Iterators.concat(lines.subList(start, lines.size()).iterator(),
                    lines.subList(0, start).iterator());
        }
    }

    public int getMaxSize() {
        return size;
    }

    public int getSize() {
        return lines.size();
    }

}
